Pyrrole carbonitrile, nitropyrrole, arylpyrrole, bisarylpyrrole, thioalkylpyrrole, alkylsulfonyl pyrrole, alkylsulfinylpyrrole thiocarboxamide pyrrole and heteroarylpyrrole compounds and derivatives thereof are highly effective insecticidal, acaricidal, nematocidal, molluscicidal and endecticidal agents useful in both plant and animal science. In general, the above-mentioned pyrrole derivatives having an alkoxymethyl substituent on the pyrrole ring Nitrogen atom are more efficacious than the parent pyrrole compounds.
The alkoxymethylation of pyrroles on Nitrogen to form N-(alkoxymethyl)pyrrole is generally achieved by the condensation of the appropriate pyrrole with an .alpha.-halomethyl ether in the presence of a strong base such as sodium hydride [i.e. J. Muchowski, et al, Journal of Organic Chemistry, 49 (1), p. 203 (1984)] or potassium t-butoxide (i.e. U.S. Pat. No. 5,010,098). However, the use of .alpha.-halomethyl ethers is not desirable in commercial or pilot plant scale production due to the severe carcinogenic properties of said ethers. Further, large scale employment of strong bases such as metal hydrides or t-butoxides is costly and hazardous.
The use of an alkylal and Vilsmeier reagent is known to give an alkoxymethyl ether of a phenolic hydroxyl group such as the process described in U.S. Pat. No. 4,500,738. However, this process is unsuccessful when applied to a pyrrole ring Nitrogen atom and no reaction takes place.
Therefore, it is an object of this invention to provide a safe and effective method for the preparation of N-(alkoxymethyl)pyrroles without the separate preparation of and handling of .alpha.-halomethyl ethers.
It is another object of this invention to provide a method for the alkoxymethylation of pyrroles without the use of strong bases such as metal hydrides or metal t-butoxides.
It is a further object of this invention to provide a readily available source of the N-alkoxymethyl derivatives of a wide variety of important pesticidal pyrrole compounds. Still further objects and features of the invention will become apparent from the description set forth below.